Process of obtaining calcium-fluorid precipitate



.40 tion of the fiuorid" ion in the concentrated PATENT OFFICE.

I WALLACE S. CHASE, OF LAKEWOOD, QHIQ ASSIGNOR, BY MESNE ASSIGNMENTS, T NATIONAL CARBON COMPANY, INC, A CORPORATION OF NEW YORK.

PROCESS OF OBTAINING CALCIUM-FLUORID PRECIPITA'IE.

No Drawing.

To all whom it may concern: J

Be it known that I, WALLACE SQCHAsE,

4 a subject Ofmthfl King of Great Britain, re-

sidingat Lakewood, in the county of Guyahoga and State of Ohio, have invented a certain new and useful- Improvement in Processes of Obtaining Calcium-Fluorid Precipitate, ofwhich the following is a full, clear, and exact description.

This invention relates to processes for (producing calcium fluorid.

in filtering and washing the precipitate on '15 In' prior processes of producing calcium fluorid great difficulty has been ezgperlenced account of its slimy character. I have discovered a process for precipitating calcium fiuorid of such character that it settles rapidly and is capable of being readlly filtered and washed. i

In the prior processes it has been the custom to'employ. dilute solutions to produce the precipitate, but I have found that if such solutions are concentrated the physical characteristics of the precipitate are altered to an extent which permits it to settle much more readily, and also to be filtered more ing equation I believe this change in form of the procipi tate is due mostly to the low concentrasolution. ,Hydrogen fluorid is a gas having the formula H 1? and when this is passe into water it dissolves and dissociates into '45.

the form HF in accordance with the followmg equation This dissociation proceeds until equilibe a rium is established and in concentrated solutions it will proceed to a less extent The double molecules of hydrofluoric acid are not only slightly dissociated inconcentrated solutions, into single molecules, but these S111- gle molecules are but shghtly dissociated Specification of Letters Patent. Patgnted Jan, 27, 1920, Application filed March 1,1917. Serial No. 151,658.

into hydrogen and fluorin ions even in dilute solutions.

Therefore, in concentrated solutions of this acid the low concentration of single molecules, HF, will result in a very low concentration of fiuorin ions, so that the interaction between these and the calcium ions .proceeds relatively slowly,.th us causing a decided improvement in the physical characteristics of the precipitate.

After the precipitate is formed it is filtered and washed in well known ways and may besu-bjected to further processes, dependmg upon its intended use.

I have also found that this precipitate can be washed and filtered much better if it is dried out by heating at a temperature preferably between 100 and 150 C. The heating will be carried on until the mass is completely dried and then it is pulverized and washed in any way,.such as by decantation wlth water to which a little hydrofluoric acidhas been added to re-form calcium fluorid from any calcium chlorid that may have been produced during the heating operatlon.

I have mentioned above certain limits of temperature to be observed in heating the slimy calcium fiuorid mass, but it will be understood that these need not be strictly adhered to in all cases. The object of the pr0cess is to heat the mass until it dries into a mass capable of being washed and filtered. Higher temperatures may be used, but detrimental reactions may result, such as the reformation to a slight extent of calciuni'chlorid, if the temperature is elevated much above 150.

The-slimy precipitate of calcium fluorid, as well as fluorids of rare-earth metals, obtained by prior processes, can also be readily washed and filtered by drying in the way just described.

The drying process, however, is not to be limited to sllmy precipitates of calcium and the rare-earth metals, as it can be used in gonnection with various other slimy precipiates."

Having described my invention, what I claim is:

1. The process of preparing insoluble fluorids of metals which consists in adding a concentrated solution of other compounds of said metals to a'concentrated solution of hydrofluoric acid.

2. The processof preparing calcium fluorid which consists in adding a highly concentrated solution of a salt of calcium to a highly concentrated solution of hydrofluoric acid.

3. The process of preparing calicum fluorid Which consists in adding a highly concentrated solution of calcium chlorid to a i hi hl concentrated solution of h drofluorlc acid- 4. The process of preparing calcium fi orid, Which consists in adding a concentrated solution otcalcium chlorid to a highly concentra ted solution of hydrofluoric acid,

evaporating to dryness, pulverizing the dried mass, and then washing 1t free of soluble material.

The process of preparing calcium flu-i orid, which consists in adding a concentrated solution of calcium chlorid to a highly concentrated solution of evaporating to dryness, pulverizing the dried mass, and then Washing it free of soluble material with Water containing hydrofluoric acldi In testimony whereof,

I hereunto affix my signature. v WALLACE S. CHASE;

hydrofluoric acid, I 

